How to model compression-dilation-compression vertical deformation behaviour during direct shear test?

Asked by Nicholas Ng on 2019-07-09

Hi all,

I'm currently using Yade to try simulate a direct shear test simulation, and benchmark against the lab results in [1]. The particles I used in my simulation are spheres. Before this, I have read at a lot of research papers about DEM simulation for direct shear test, and most of the papers emphasizes a lot on how to calibrate the micro-parameters to get the intended response for shear stress vs shear displacement plot, but there is very little information about how to calibrate DEM simulation to match the lab result of vertical deformation vs shear displacement plot.

My problem now is when I run my direct shear test simulation in Yade, and later look at the vertical deformation vs shear displacement result, the behaviour is like compression-dilation behaviour, and not matching the lab result in [1] of compression-dilation-compression behaviour. At first I suspect maybe it's because I used spheres in simulation (real life particles are not perfectly spherical), that's why it result in excessive dilation. However, when I go through other research papers, I notice it may not be particle shape that is causing this, because different papers I read, whether it's using spherical or non-spherical particles, it seems the typical vertical deformation behaviour from DEM simulation is compression-dilation. Some papers I referred to are [2] for spherical particles, and [3] for non-spherical particles.

I have reasoned out that for [2] and [3] the DEM simulation and lab direct shear test can be compared because both methods the vertical deformation behaviour show compression-dilation pattern. However, my research now is to simulate the lab direct shear test result of material in my area, which is as enclosed in [1], and the vertical deformation pattern is compression-dilation-compression, which I still had not found in any DEM simulation papers yet.

I hope someone can give me some hints or advice on which micro-parameter or which contact model should I change in DEM to match this vertical deformation pattern of compression-dilation-compression.

I greatly appreciate any advice to be given based on this problem of mine.

[1] https://www.jstage.jst.go.jp/article/jgssp/2/8/2_MYS-06/_article/-char/en [pg 356]
[2] https://www.sciencedirect.com/science/article/pii/S0266352X15000488 [pg 87]
[3] https://ascelibrary.org/doi/full/10.1061/%28ASCE%29GM.1943-5622.0000264 [pg 37]

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2019-07-09
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2019-07-24
Launchpad Janitor (janitor) said : #1

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